Method for the manufacture of collagen tape



y 2,1970 E. BbRYSKo ET AL 3,511,397

METHOD FOR THE MANUFACTURE OF COLLAGEN TAPE Filed Nov. 16, 1967 ENTORSI F/v/z EMT/K0 Somerville, and

5 Claims ABSTRACT OF THE DISCLOSURE In the manufacture of a collagen tape which may be twisted to form a round strand that is useful as an absorbable surgical suture, an acid dispersion of collagen fibrils is extruded into a dehydrating bath to form a multifilament. The multifilament, While still wet from the dehydrating bath, is compressed to form a ribbonlike tape in two or more steps by passage between two or more sets of squeeze rolls, the space between succeeding sets of rolls decreasing so that the compression of the multifilament is accomplished in two or more increments. A certain amount of stretch is imparted to the tape as it passes between the sets of squeeze rolls to assist in the orientation of the collagen fibrils. By varying the total compression of the wet multifilament, the width and thickness of the tape can be controlled providing that the wet tape is dried in a controlled manner and simultaneously given additional stretch in small increments by passing the tape in a sinusoidal path around a series of driven godets, each revolving at a greater peripheral speed than the preceding godet in the series.

BACKGROUND OF THE INVENTION This invention relates to strand-like materials, such as, absorbable sutures and ligatures, made from collagen fibrils. More specifically, the present invention is an improvement in the method of producing a collagen strand as described in US. Pat. No. 3,114,593.

The aforesaid patent describes the continuous extrusion of a homogeneous dispersion of pure swollen collagen fibrils into a dehydrating bath to form a bonded multifilament tape that is further processed, for example, by tanning, twisting, and stretching in proper sequence to obtain a round strand of uniform diameter and physical properties having utility as an absorbable suture. The method for manufacturing a continuous length of a ribbon-like collagen tape wherein the individual filaments that make up the tape cohere together to form a unitary structure is described in Example X and is illustrated in FIG. 28 of Pat. No. 3,114,593.

It is a disadvantage of the manufacturing process described that precise control of the width and thickness of the tape is difiicult to achieve, and variations in excess of ten percent in these dimensions may be experienced. Such variations have a profound effect on tannage penetration which is dependent on the relationship of the surface area to volume. Variations in the width and thickness of the tape also elfect the roundness and coherence of the finished strand, which is dependent on the number of turns that are required to roll the flat tape into the finished round string.

Another disadvantage of the manufacturing process described is that the tapes produced may sometimes be too narrow and thick for subsequent processing.

It is an advantage of the improved process to be described that precise control of tape dimensions can be maintained.

It is an additional advantage of the improved process United States Patent 0 to be described that tape production speeds can be increased.

It is an additional advantage of the improved process to be described that it permits the manufacture of a thinner, wider tape than that obtained by the process described in US. Pat. No. 3,114,593.

It is an additional advantage of the improved process to be described that it practically eliminates breakage of the tape during the stretching procedure.

SUMMARY OF THE INVENTION In accordance with the present invention, the extruded collagen multifilament is passed between a first driven godet and a first squeeze roll and compressed to form a ribbon-like tape, the amount of compression being controlled by the space between the driven godet and squeeze roll. The resultant Wet tape is then passed to a second driven godet and a second squeeze roll with some stretching to assist in orienting the collagen fibrils, where it is again compressed by virtue of the space between the second driven godet and second squeeze roll being less than the space between the first godet and first squeeze roll.

This process of compressing and stretching the tape may be repeated as often as desired. The end product is a well-bonded, wet tape consisting of highly-oriented, partially swollen collagen fibrils and containing essentially no free fluid. The tape is then further stretched and dried in a controlled manner by passing it in a sinusoidal path around a series of driven godets, each of which revolves at a slightly greater peripheral speed than the preceding godet so that the tape is stretched in small increments between the godets as it dries. Final drying of the tape to equilibrium with ambient relative humidity is accomplished by passing the tape many times between a driven godet and an idler roll. The dried tape is then collected continuously on a take-up drum (spool). In this manner, a tape of the desired width and thickness, consisting of highly-oriented collagen fibrils, is produced with essentially no machine down time due to breakage.

For a more complete understanding of the invention, reference should be made to the accompanying drawing which illustrates a method of continuously squeezing and stretching in small increments an extruded collagen tape as it is transported from the dehydrating bath to a takeup drum.

BRIEF DESCRIPTION OF THE DRAWING Referring now to the drawing for an understanding of the physical handling steps and the apparatus employed, a wet, extruded collagen multifilament 10 passes from the dehydrating bath 12 and over the driven godet 14. A squeeze roller 16 in rolling contact with the godet 14 flattens the wet multifilament by a controlled amount and removes excess liquid therefrom. The wet multifilament in passing over the godet 14 under the pressure of the roller 16 is bonded together to form a ribbon-like tape. The tape from the godet 14 passes around the idler roller 18 and over the driven godet 20 which may rotate more rapidly than the godet 14 stretching the tape. The tape is again compressed by a controlled amount as it passes over the godet 20 by a second squeeze roller 22 which removes additional liquid from the tape. The process of alternately compressing and stretching the tape may be repeated as often as desired. The tape from the godet 20 next contacts a series of driven godets that follow the second squeeze roller 22 (or the final squeeze roll, should more than two sets of squeeze rolls be used). The godets 32, 34, 36, and 38 are in alignment and are separated by a distance that is approximately equal to the radius of the godet so that the tape in passing around each godet in the series describes a sinusoidal path and is in contact with the periphery of each godet over a substantial distance. Each godet in the series rotates in the direction indicated by the arrow (in the direction that the tape is moving), and each godet rotates at an angular velocity greater than that of the preceding godet in the series. Thus godet 34 rotates more rapidly than godet 32 and imparts a slight controlled stretch to the tape as it passes between the point 40 on the circumference of godet 32 and the point 41 on the circumference of godet 34. In like manner, godet 36 rotates more rapidly than godet 34 imparting a slight stretch to the tape as it travels therebetween, and the godet 38 rotates more rapidly than the godet which precedes it in the series. It will be noted that the godet 38 is somewhat larger in diameter than godet 36. It will be obvious that the differential stretch is applied to the tape by increasing the peripheral speed of succesive godets that contact the tape and this may be accomplished by either increasing the diameter of successive godets in the linear array, increasing the angular velocity of rotation of successive godets, or increasing both the diameter and angular velocity.

The bonded and stretched tape from the godet 38 passes around idler rollers 24, 42, and idler roller 43 before being collected on the driven godet 26 and its associated godet 28 for further drying. The drying tape from the godet 28 passes over idler roller 31 and is continuously collected on the take-up drum 30.

DESCRIPTION OF THE PREFERRED EMBODIMENT Example I A dispersion of acid-swollen collagen fibrils in an aqueous methanol cyanoacetic acid solution is prepared as described in Example X of Pat. No. 3,114,593. This collagen dispersion is extruded through a stainless steel spinnerette, drilled with 192 openings arranged in concentric circles into an acetone dehydrating bath 12 containing 130 mg. of ammonia and 50 g. of water per liter. The extruded multifilament is squeezed a controlled amount by adjusting the clearance between the driven godet 14 and the Squeeze roller 16 to remove excess acetone and ammonia and compress and bond the individual filaments into a unitary ribbon-like tape. The collagen tape from the godet 14 .passes around the idler roller 18 and is squeezed by a controlled amount between the driven godet 20 and a second squeeze roller 22, which presses additional liquid from the tape and reduces the thickness of the collagen tape. The godet 20 is of the same diameter as godet 14 but rotates at an angular velocity that is 7 /2 percent greater than that of godet 14 thereby producing a stretch of 7 /2 percent in the collagen tape as it moves between the godet 14 and the godet 20. Additional stretch is applied to the collagen tape as it moves over the surface of godets 32, 34, 36, and 38. Each godet in the series rotates at a peripheral velocity about percent greater than that of the preceding godet in the series. Thus if the peripheral velocity of godet 34 is 5 percent greater than the peripheral velocity of godet 32, a 5 percent stretch will be applied between the points 40 and 41; an additional 5 percent stretch is applied between godets 34 and 36; and an additional stretch of 5 percent occurs between godets 36 and 38. Thus a total stretch of about percent is ap plied to that length of tape that is moving between the godets 32 and 38.

The stretched collagen tape is air dried as it moves over the rollers 24, 42, 43, and passes between the driven godet 26 and the idler roller 28, and is collected in its dry state at equilibrium with ambient relative humidity on the take-up drum 30. The collagen tape collected on the take-up drum 30 is about 100 mils in width and about 3 nails in thickness. It may be processed as described 4 in Example XI of Pat. No. 3,114,593 to obtain a collagen strand that has a diameter of 15.0 mils (1270 denier), a dry tensile strength of 4.2 grams per denier, a dry knot strength of 2.3 grams per denier, and a wet knot strength of 1.35 grams per denier.

A thin cross-section of this strand upon microscopic examination resembles the strand prepared in accordance with Example XI of U.S. Pat. No. 3,114,593 in that it resembles a jelly roll, the collagen ribbon or tape being rolled upon itself. Because the tape is thinner and wider than the tape prepared in accordance with Example X of the above-mentioned patent, however, there are more convolutions of the tape that form the strand.

It should be understood that the above description has been made with reference to the preferred embodiment illustrated in the drawing and that modifications and alterations can be made therein without departing from the invention except as expressly limited hereafter in the claims.

What is claimed is:

1. In the manufacture of a collagen tape by the continuous extrusion of an acid dispersion of collagen fibrils to form a multifilament wherein the multifilament is passed between a driven godet and a first squeeze roller to form a ribbon-like tape in which the individual filaments cohere and the tape is stretched while Wet and dried, the improvement which comprises:

stretching the tape as it passes between said first squeeze roller and a second squeeze roller, and contacting the tape sequentially with the periphery of a series of driven godets, each of which is revolving at a peripheral velocity greater than that of the preceding godet in said series, whereby said tape is stretched in small no greater than 7% percent increments as it passes from one godet to another.

2. The method of claim 1, wherein each godet in said series is of the same diameter and revolves at an angular velocity greater than that of the preceding godet in the serles.

3. In the method of claim 1, wherein each godet in said series revolves at the same angular velocity and has a diameter greater than that of the preceding godet in the series.

4. In the manufacture of a collagen tape by the continuous extrusion of an acid dispersion of collagen fibrils into a dehydrating bath to form a multifilament wherein the multifilament as it leaves the dehydrating bath is passed between a driven godet and a first squeeze roller to form a ribbon-like tape in which the individual filaments cohere and the tape is stretched while wet and dried, the improvement which comprises:

stretching the tape as it passes between said first squeeze roller and a second squeeze roller and imparting additional stretch to the tape in small no greater than 7 /2 percent increments as it moves away from the second squeeze roller by contacting the tape at frequent intervals with a plurality of godets, each of which revolves in the direction that the tape is moving at an increasing peripheral speed.

5. In the manufacture of a collagen tape by the continuous extrusion of an acid dispersion of collagen fibrils to form a multifilament wherein the multifilament is passed between a driven godet and a first squeeze roller to form a ribbon-like tape in which the individual filaments cohere and the tape is stretched While Wet and dried, the improvement which comprises:

stretching the tape as it passes between said first squeeze roller and a second squeeze roller, and

stretching the tape in small no greater than 7 /2 percent increments by passing it in a sinusoidal path around a series of successive driven godets, each of which revolves at a greater peripheral speed than the preceding godet in the series.

(References on following page) References Cited UNITED STATES PATENTS 6 FOREIGN PATENTS 163,803 7/1955 Australia. Dumont 1,107,038 5/19-56- France. 5332 13:11:11: 3221385 5 JULIUS FROME, Primary Examiner BOTYZYKOWSKi 2 J. H. WOO, Assistant Examiner Hooper 264-182 X Walt r 2649 US. Cl. X.R. Mummery. 264210 Nichols et a1. 264-202 X 10 Bull 61 a1. 117-74 X Jamieson 264341 X UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,511, 337 Dated May 12, 1970 Inventor) Emil horyske, Arthur A. Gertzman and Ernest J. Griset, Jr.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[- In column 4, lines 3 and 3 lines 5&- and 55, and lines 69 and 70, the word "increments" should be deleted after the word "percent" and inserted after the word "small". In the References Cited, the name "Kadf" should read Kadt Also, the French reference should read 1,117,038 instead SIGNED MW SEALED SE P 2 9 1970 Aucat:

ard M. Flewher, I1".

Amsting Officer WILLIAM 1:. JR.

".omissioner of Patents 

